Touch panels generally operate as follows. When a finger or other object touches a screen, voltage, current, acoustic waves or infrared rays are detected depending on different sensing manners so as to determine coordinates of the position where the touch point is located. For example, for a resistive touch panel, the position of a touch point is determined by calculating the position of the pressed point using a potential difference between upper and lower electrodes. For a capacitive touch panel, capacitive changes resulted from electrostatic contact between transparent electrodes and human body occur, and the coordinates of touch points are detected according to current or voltage generated due to the capacitive changes.
In old technologies, a capacitive touch panel is disposed on a liquid crystal panel. At present, integration of the capacitive touch panel and the liquid crystal panel has become more popular. The integration of the touch panel and the liquid crystal panel includes an “in-cell” method and a “on-cell” method. The “in-cell” method refers to that the touch panel function is embedded into the liquid crystal pixels. The “on-cell” method refers to embedding the touch panel function between a color filter substrate and a polarization sheet.
In the in-cell mode in which the touch panel and the liquid crystal panel are integrated, the capacitance of the touch panel is easily interfered by OLED circuits, and sometimes capacitance of electrodes associated with a whole string electrode can be raised a lot, and thus touch points cannot be identified accurately. The noise is resulted from the OLED display images. As shown in FIG. 1, a driving circuit 2′ and a sensing circuit 3′ are provided at periphery of a touch panel 1′. Driving lines 21′ and sensing lines 31′ are disposed on the touch panel 1′, capacitors are provided between the driving lines and the sensing lines. The driving circuit 2′ drives the driving lines on the touch panel 1′, and the sensing circuit 3′ senses signals of the sensing lines on the touch panel 1′. The conductive lines on the touch panel 1′ which are connected with the driving circuit 2′ and oriented in a first direction (X direction) are the driving lines 21′, and the conductive lines on the touch panel 1′ which are connected with the sensing circuit 3′ and oriented in a second direction (Y direction) are the driving lines 31′. Capacitors are connected between the driving lines 21′ and the sending lines 31′. During the former half of each period, the driving circuit 2′ drives the conductive lines 21′ oriented in the first direction, and the conductive lines 21′ charge the capacitors using voltage. During the latter half of each period, the sensing circuit 3′ senses the voltage on all of the conductive lines 31′ oriented in the second direction to obtain n data. After m driving periods, m×n data can be obtained.
However, when a finger touches a position A on the touch panel 1′, touch noise resulted from the interference of circuits occurs, and the sensing circuit 3′ will sense a connection signal Li (Li=Si+Ni) including a normal signal Si and a noise signal Ni. Thus, sensing error occurs, thereby influence the sensing accuracy of the capacitive touch panel 1′.
In view of the above, inventors of the present disclosure provide a method for filtering touch noise and a touch device.